A projection plane (screen) usually refers to a surface which reflects the light or makes the light beam visible due to different type of scattering or/and absorption. In particular, the phenomenon of Mie scattering of light by spherical particles of any diameter allows creating a projection screen in air by spraying the mist, gas, liquid or a specific substance (snow, dust or the like).
Similarly, a projection volume refers to a three-dimensional object which reflects the light or makes the light beam visible as a 3D pattern due to different type of scattering or/and absorption.
In particular, the 3D display system as disclosed in U.S. Pat. No. 8,567,954-B uses a planar sheet of mist or water droplets as a rear projection screen and a suitable optical filtering mechanism for projecting and viewing the 3D content, for projector and both eyes of a viewer. The screen is substantially planar and has a front surface facing a viewing area and an opposite rear surface.
In another system disclosed in U.S. Pat. No. 8,511,828-B, the authors proposed to arrange a plurality of nozzles ejected water fountains to produce a water mist onto which the projector projects images. The controller is able to synchronize the projector and, at least, one of a plurality of nozzles to produce a water mist in a sequence such that the images have appeared at different distances from the projector at different times. The controller may further control the orientation of each nozzle to vary the distance by inclining the plane of the water mist relative to the surface of the body of water. Such the installation could work well for public sites such as hotels, amusement parks, and shopping centers where there is enough space for a big water reservoir (as a fountain or a swimming pool or the like), when an extra humidity even improves the ambient conditions. However, the solution like this or disclosed in U.S. Pat. No. 5,067,653-A are not appropriate for a portable desktop installation, for projection and interaction with 3D graphic content.
Some efforts have already been undertaken by different companies to develop a realistic 3D display. However, any technology exhibits limitations.
For instance, Heliodisplay Mid-air projection system disclosed in US-2004/0001182-A or U.S. Pat. No. 6,857,746-B are actually able to shape a flat projection screen and consequently only 2D projections on a scattering surface of the water mist condensed from air. Nevertheless, the Heliodisplay prices range from $39,000 USD for a model L to $66,000 USD for a model XL that does not correspond to a limited functionality of the system.
In the system disclosed in US-2011/0285964-A, it was proposed to create the projection screen with the use of snowmaking machine. The flowing snow is output in a substantially planar thin sheet by imitating the regular screens manufactured from different materials such as fabrics, painted wood, metal, plastic, or other solid substance. Like in many other approaches (U.S. Pat. No. 5,445,322-A, U.S. Pat. No. 5,368,228-A, U.S. Pat. No. 5,265,802-A and U.S. Pat. No. 3,334,816-A), by shaping the planar scattering screen surface, the systems do not allow to display the realistic 3D images viewed by naked eyes from a different viewing angle.
The Holodust system (U.S. Pat. No. 6,997,558-B) is a true open-air volumetric display based on detection of dust particles, stochastically distributed over a limited volume, by rapidly sweeping infrared laser and highlighting/‘lighting up’ by the second (color) laser (coaxial to the invisible one) only the particles (voxels) in the positions that correspond to the simulated 3D model. Nevertheless, the authors have been more focused on the method of selective illuminating the particles and not on the way of suspending light scattering particles properly in the volume. It was only mentioned that the dust particles could be relatively large particles of fabrics (such as lint, wool or similar) of about 0.5-1.0 mm in length and the cloud of particles should be not visible to an unaided eye under normal lighting conditions. While the quality of 3D images might significantly be improved with the use of vector-oriented graphic drawing method for laser-scanned display (Halabi, O. et al. “Efficient vector-oriented graphic drawing method for laser-scanned display” Displays, 2009, 30, 97-106 and WO-2008-126018-A), the system used in the prototype for creating suspending particles was cumbersome and failed to be produced in a compact form factor.
Instead of the dust generator it would be possible to use any other solution as disclosed, for example, in U.S. Pat. No. 6,819,487-B, U.S. Pat. No. 5,270,752-A or Plasencia, D. M. et al. “MisTable: reachthrough personal screens for tabletops” Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, 2014, 3493-3502 (doi>10.1145/2556288.2557325). However, while these techniques are able to create a projection volume, these techniques are bulky as the Holodust system (U.S. Pat. No. 6,997,558-B). Even if it would be possible to produce with a limited functionality any of proposed mist generators in a compact form factor, the method disclosed in the mentioned patents cannot support many new emerging demands (e.g., US-2004/0001182-A). Because a higher density mist in the whole volume will obscure and distort a larger part of the 3D content, while a low density mist could allow to display only primitive graphics with a poor resolution, as translucent images will overlap and interfere with each other.
Nowadays, there are many techniques and variants of creating stereoscopic and holographic images as well as producing commercial displays/monitors which allow an observer with two naked eyes to perceive two different images, when the observer is looking into a display screen and no glasses is required. However, there is no mist/fog based display that could be able to display objects in thin air as 3D images, that is an observer would be able to view with two naked eyes different content from a different viewing angle. The illusion images, which many authors claimed as 3D, actually present a planar (2D) image projection over the “shell” (the outer layers) of the high-density scattering screen surface or volume and do not allow to simultaneously project/reflect multiple projections in depth. As the mist/fog/fluid presents a translucent substance which will interfere overlapped images or obscure their parts (see references mentioned above).
The solutions that have been already realized were targeted to improve quality of the projected planar images by increasing density and stabilizing the planar scattering screen surface or volume. However, the more scattering screen is stable and less transparent the more time is required with known techniques (which are based on ejection a laminar air flow) to alter a spatial location of the scattering centers from one slice of 3D volume to another one. To display a sequence of the plurality of multiple images or slices in a volumetric region which will not overlap and interfere, the scattering volumes/surfaces should immediately disappear after the frame was highlighted using the method disclosed in Halabi, O. et al. “Efficient vector-oriented graphic drawing method for laser-scanned display” Displays, 2009, 30, 97-106, U.S. Pat. No. 6,997,558-B, WO-2008-126018-A or the like.